This invention relates to a cleaning device for a photoelectric receptor, particularly to a device for removing residual magnetic toner particles left on the photoelectric sheet after a toner image has been transferred from the photoelectric sheet to another sheet such as plain paper and to a process for such removal of toner particles.
A customary photoelectric duplicating process includes: uniformly charging the surface of a photoreceptor by a corona charger or the like; exposing the charged surface to a light image which is to be duplicated; adhering toner particles to the surface to make a toner image; and transferring the toner image to another sheet. In order to repeat this process, it is necessary to remove the residual toner left on the photoreceptor after the transfer step. Various cleaning means and methods have been developed previously.
A typical cleaning process is that the residual toner is scraped off by a rubber blade. But, in this process the photosensitive surface of the photoreceptor tends to be scratched by the scraping.
Another typical cleaning method includes the use of a fur brush which has animal fur attached to a rotatable shaft in such a manner that the tips of the fur form a cylinder. In order to remove completely the residual toner by the fur brush, the fur brush contacts the surface of the photoreceptor with a certain strength. This strong contact causes damage to the photoreceptor and the fur brush, so that it is necessary to renew them frequently. Furthermore, in the latter process, it is necessary to gather the removed toner by suction after removing the toner from the photoreceptor. Instead of gathering excess toner by suction, Suzuki et al, Japanese laid open patent publication No. 52-13343 published Feb. 1, 1977, proposed a cleaning method that, after removing the residual toner by a fur brush, the toner adhered on the fur brush is removed by a magnetic roll and subsequently the toner on the magnetic roll is gathered by a scraper blade.
Cleaning methods using a magnetic brush have been proposed to eliminate drawbacks in the use of the fur brush. For example, Ohnuma et al, Japanese laid open patent publication No. 52-86337 published July 18, 1977, discloses that residual one-component magnetic toner left on a photoreceptor can be removed by a magnetic brush formed on a magnetic roll which is similar to one which is used to develop a latent image. To remove residual magnetic toner by the magnetic brush, a certain amount of magnetic toner is adhered on a magnetic roll to form the magnetic brush of the toner and the magnetic brush sweeps the residual toner left on a photoreceptor to adhere the residual toner to the magnetic brush. Such magnetic brushing methods have an advantage that residual toner can be removed with an extremely soft contact with the surface of a photoreceptor and the possibility of scratching the photoreceptor is eliminated. However, a certain amount of toner usually contacts the surface of the photoreceptor so that the toner tends to agglomerate or to form cakes. In addition, the direct contact between the magnetic brush and the photoreceptor is disadvantageous because the life of the photoreceptor, especially the surface of zinc oxide-coated paper, is adversely affected by the continued contact.
The term "magnetic roll" or "magnet roll" is well known by those of ordinary skill in the art. The constructions of magnetic rolls are disclosed, for example, in Yamashita et al U.S. Pat. No. 3,828,730 and Anderson U.S. Pat. No. 3,455,276. It is not necessary to explain developing processes using one-component magnetic toner, since the various processes are shown, for example, in Kotz U.S. Pat. No. 3,909,258 and Nishihama et al U.S. Pat. No. 4,081,571.